Fujitsu MB90895 Series Hardware Manual page 558

CHAPTER 16 CAN controller
G
Starting reception
Reception is started when the start-of-frame (SOF) of a data frame or remote frame is detected on the CAN
bus.
G
Acceptance filter
The received message in the standard frame format is compared with the message buffer (x) set in the
standard frame format (IDER: IDEx = 0).The received message in the extended frame format is compared
with the message buffer (x) set in the extended frame format (IDER: IDEx = 1).
Passing through the acceptance filter
If all bits set to compare in the acceptance mask are matched after "comparison" between the received
message ID and acceptance code (IDR: IDx), the received message passes the acceptance filter in the
message buffer (x).
G
Storing received message
If message reception is successful, the received message is stored in the message buffer (x) that has the ID
that had passed the acceptance filter.
Data frame received
The received message is stored in the ID register (IDR) and DLC register (DLCR), data register
(DTR).If the received message is less than 8 bytes, undefined data is stored in the rest of the bytes in the
data register (DTR).
Remote frame received
The received message is stored in the ID register (IDR) and DLC register (DLCR).The data register
(DTR) remains unchanged.
More than one message buffer
If there is more than one message buffer with the ID that had passed the acceptance filter, the message
buffer (x) where the received message is stored is determined under the following conditions:
• Higher priority is given to the message buffer with a smaller number (x = 0 to 7).The priority of
message buffer 0 is the highest and 7 is the lowest.
• The received message is stored in preference to the message buffer that has not been completed
receiving (RCR: RCx = 0).
• If the bit in the acceptance mask select register is set to "full-bit comparison" (AMSx.1 = 0, 0 = "00
the received message is stored in the corresponding message buffer (x), regardless of the setting value of
the reception complete register (RCR: RCx).
• If there is more than one message buffer that has not been completed receiving, or if there is more than
one message buffer with the AMSx.1 and AMSx.0 bits in the acceptance mask select register set to 00 B
(full-bit comparison), the received message is stored in the message buffer with the smallest number (x).
• If there is no message buffer that satisfies the above conditions, the received message is stored in the
message buffer with the lowest number (x).
540
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B